Leakage of confidential information such as personal and sensitive information is a major social issue today. Corporations and public organizations save and manage confidential information on data servers or the like that can be accessed by people over networks. Leakage of such confidential information is prevented by setting various kinds of access right to electronic documents including confidential information to limit access to them.
It is a common practice to create a new electronic document by utilizing content data replicated from an existing electronic document. However, preparation of a new electronic document utilizing an existing electronic document containing confidential information can lead to leakage of confidential information through replication of context data included in the existing document. To address this, various techniques for preventing leakage of confidential information have been proposed.
Patent Literature 1 discloses a method for preventing information leakage by storing copied data with encryption in a clipboard and decrypting the copied data at a target document. In this method, in the case of a source document that should be protected, copied data is sent to the target document if the target document is also a protected document, while dummy data is sent to the target document if the target document is a document not requiring protection, thereby preventing information leakage.
Patent Literature 2 discloses a method for controlling document copy by means of a clipboard with separate areas to save copied data for important documents and general documents. According to the method, if the source document is an important document, specified copied data is saved in a clipboard for important documents. If the target document is an important document, the copied data is read from the clipboard for important documents and pasted. If the target document is a general document, read of the copied data from the clipboard for important documents is prohibited to prevent leakage of an important document.
Patent Literature 3 discloses an electronic document management apparatus that controls access to data saved in a clipboard and authentication information when an electronic document that should be protected is used to create another electronic document. This electronic document management apparatus prevents information leakage by allowing access authority for the protected source electronic document to be inherited to the target electronic document.